1. Field of the Invention
The present disclosure relates to processing communication data. In particular, but not exclusively, the present disclosure relates to processing communication status information in a telecommunications network.
2. Description of the Related Technology
In telecommunications networks, communications sessions, such as voice calls and video calls, may be established between endpoints via the network. Such endpoints may for example include mobile telephones, fixed line telephones and personal computers. Additionally, event based services, such as registration, messaging and presence services may also be provided. In order to ensure that such communication sessions and event based services are billed accurately, a telecommunications network typically includes a charging node responsible for monitoring the establishment and duration of communication sessions and the occurrence of event based services. Communication sessions are typically billed according to session based billing, in which the start and end of the session are reported to the charging node, with interim messages being reported periodically to confirm that the session is still ongoing. In contrast, event based services are typically billed according to event billing, in which event messages are reported to the charging node upon occurrence of the event.
Internet Protocol (IP) telephony networks, such as those conforming to the IP Multimedia Subsystem (IMS) are currently experiencing an increase in prevalence. In such networks, telephony services are typically provided according to the Session Initiation Protocol (SIP). An IP telephony network may contain a number of signaling nodes which are each responsible for carrying out one or more signaling functions in the network, such as conducting registration procedures, handling routing requests and/or handling service requests. In the case of IMS, a signaling node may fulfil the role of a Call Session Control Function (CSCF). In the context of SIP, such a signaling node may fulfil the role of a SIP server and/or a SIP proxy.
Signaling nodes may therefore maintain state information (for example routing data, authentication data etc.) for each subscriber that they serve. For relatively small numbers of subscribers, it may be practical for each signaling node to maintain state information for every subscriber. However, for large numbers of subscribers, the memory and associated processing requirements for storing state information for every subscriber at each signaling node and the requirement for replicating the state information between all signaling nodes in the network can become prohibitive.
In order to cater for a larger number of subscribers, known sharding techniques can be employed in IMS networks. Sharding involves allocating a longstanding responsibility for a subset of the subscribers in the telecommunications network to each signaling node in the network. Each signaling node therefore need only maintain state information for its allocated subset of subscribers. In a typical example, when a subscriber device registers with the network, it may be allocated to a signaling node, such as a Serving CSCF (S-CSCF) in the case of IMS, which is thereafter responsible for handling signaling information and maintaining the appropriate state information for that subscriber until such time as the device unregisters from the network. Similarly, a number of further signaling nodes may be utilized when a communication session is established to handle set up of that communication session as well as maintenance of the established communication session thereafter. A number of these further signaling nodes are included in the signaling path for signaling messages relating to that communication session for the duration of the communication session. In the case of IMS, these further signaling nodes may include one or more further CSCFs, for example including Interrogating CSCFs (I-CSCFs), Proxy CSCFs (P-CSCFs) and further S-CSCFs, as well as Border Gateway Control Functions (BGCFs), Interconnection Border Control Functions (IBCFs), Media Gateway Control Functions (MGCFs) etc.
However, this sharding approach suffers from increased routing complexity because any signaling messages (for example, in relation to establishment of a communication session) relating to a given subscriber that are handled after the initial registration must be routed via the appropriate, sharded network node. Further, the complexity of providing redundancy between sharded network nodes in order to handle failure of an individual network node in the network is increased. Hence, it would be desirable to provide improved and/or alternative techniques for handling potentially large numbers of subscribers and/or providing the required network scalability to do so, whilst providing measures which enable charging of communication sessions which are compatible with such techniques.